1. Field of the Invention
The present invention relates to a storage device utilizing movement of particles between electrodes.
2. Description of the Related Art
With the recent increase in the degree of integration of semiconductor devices, continuous effort has been made to reduce the sizes of circuit patterns of the LSIs constituting semiconductor devices. For a reduction in the size of the pattern, it is necessary not only to reduce line width but also to improve the dimensional and positional accuracies of the pattern. This also applies to memories, for which there has been a continuous requirement that a specified number of charges required for storage be retained in a smaller area in a cell formed using an accurate patterning technique.
Various semiconductor memories such as DRAMs, SRAMs, and flash memories have hitherto been manufactured. However, these memories employ MOSFETs as memory cells, so that the reduction in the size of the pattern is accompanied by a demand for an increase in dimensional accuracy by a percentage larger than that by which the size of the pattern is reduced. Thus, a heavy burden has also been imposed on a lithography technique for forming these patterns. This in turn has increased the cost of a lithography process accounting for the major part of the present mass production cost, that is, the product cost (OYO BUTURI, Vol. 69, No. 10, pp. 1233 to 1240, 2000, “Semiconductor memory; DRAM”, OYO BUTURI, Vol. 69, No. 12, pp. 1462 to 1466, 2000, “Flash Memory, recent Topics”).
On the other hand, techniques for fundamentally solving these problems with fine patterning include an attempt to artificially synthesize desired molecular structures and utilize the uniformity of synthesized molecules to obtain elements with uniform properties. However, serious problems remain to be solved which relate to techniques for arranging the synthesized molecules at desired positions and bringing the molecules into electrical contact with arranged electrodes. Moreover, disadvantageously, the elements use a very small number of charges for storage, so that disturbance such as natural radiation sharply increases the probability of malfunction of the elements.
As described above, for conventional memories using MOSFETs as their cells, with the reduction in the size of the pattern, very high dimensional and positional accuracies have been requested for the pattern. It is technically difficult to meet this demand while satisfying the request to avoid increasing the manufacture cost. On the other hand, memories utilizing molecular structures have problems with the manipulation of molecules and contact with the electrodes. Disturbance is also likely to cause these memories to malfunction.